Organic EL display device

ABSTRACT

In an organic EL display device, a resistance of a cathode electrode of OLEDs is substantially reduced while maintaining a higher opening ratio of pixels as an entire display area. A reference power supply line is formed on a glass substrate, and receives a reference potential for driving the OLED. The OLED is formed on the glass substrate where the reference power supply line is formed, and has a structure in which a lower electrode, an organic material layer, and an upper electrode that is a cathode electrode common to plural pixels are laminated on each other in the order from the bottom. In some of the plural pixels, a cathode contact that penetrates through the organic material layer, and electrically connects the upper electrode to the reference power supply line is formed within an opening area corresponding to a W sub-pixel.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese applicationJP2013-202935 filed on Sep. 30, 2013, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an organic electroluminescent (EL)display device, and more particularly to homogenization of a potentialof an electrode common to plural pixels arrayed in a display area amongelectrodes of organic light emitting elements.

2. Description of the Prior Art(s)

The organic EL display device has a structure in which a TFT substrateis bonded to a counter substrate. FIG. 7 is a schematically partialcross-sectional view of a display area of a TFT substrate 4 in a relatedart organic EL display device 2, which illustrates a verticalcross-section along a horizontal direction of the display area. The TFTsubstrate 4 is configured, for example, so that a circuit layer 8, aninsulating film 10, a bank 12, an organic light emitting diode (OLED)14, and a sealing film 16 are laminated on a glass substrate 6.

Plural pixels are two-dimensionally arrayed in a display area. In anorganic EL display device that conducts color display, each of thepixels includes plural sub-pixels that emit lights of different colors.For example, each of the pixels can be configured by an R sub-pixel thatemits light of red (R), a G sub-pixel that emits light of green (G), anda B sub-pixel that emits light of blue (B). One pixel is also configuredby four sub-pixels adding a W sub-pixel that emits light of white (W) tothose sub-pixels.

The OLED 14 is formed in an opening area surrounded by the bank 12(partition) for each sub-pixel, and includes a lower electrode 20, anorganic layer 22 (organic material layer), and an upper electrode 24.The lower electrode 20 and the upper electrode 24 configure an anodeelectrode (anode) and a cathode electrode (cathode) of the OLED,respectively, and light emission in the organic layer 22 is controlledaccording to an electric signal applied between those electrodes. Theupper electrode 24 is basically shared by the pixels in the overalldisplay area, connected to a feeder line on an edge of the display area,and applied with a common voltage from a drive unit. On the other hand,the lower electrode 20 is formed for each of the pixels, and suppliedwith a current corresponding to a video signal from the drive unitthrough a pixel circuit of each pixel and a drive power supply linewhich are formed in the circuit layer 8.

The bank 12 functions as a partition for partitioning the OLED,particularly the organic layer 22 for each of the sub-pixels. Also, thebank 12 is formed of an insulating layer, and prevents short-circuitingbetween the respective lower electrodes 20 formed in every opening area.

The upper electrode 24 and the lower electrode 20 are made of atransparent conductive material such as IZO (indium zinc oxide) or ITO(indium tin oxide), for example. In particular, in the organic ELdisplay device of a top emission type, it is desirable that thattransmittance of light in the upper electrode 24 is higher from theviewpoint of a reduction in the power consumption. In this example, ifthe transparent conductive material is thinned, the transmittance of theupper electrode 24 increases. On the other hand, the electricconductivity of the upper electrode 24 decreases, and a voltage dropcaused by a current that flows in the OLED increases. Specifically, apotential difference between a position closer to the feeder line and aposition farther from the feeder line in the upper electrode 24 becomeslarger. As a result, shading (luminance gradient) in which a currentdensity of the OLED decreases more to reduce the brightness more at aposition farther from the feeder line occurs. That is, there arises sucha problem that the light emission brightness does not become uniform,and display unevenness is generated within the display area. Thisproblem becomes more remarkable as an area of a display panel is larger.

Under the circumstances, a configuration in which a feeder line thatassists conduction is made of a material low in resistance value, andthe upper electrode 24 and the feeder line are connected to each otherthrough a contact hole formed in the bank 12 to substantially decreasethe resistance of the upper electrode 24 has been proposed (JP2009-199868 A).

FIGS. 8 and 9 are plan views of a part of a display area of the organicEL display device in which a contact hole 32 that connects the upperelectrode 24 and a feeder line 30 is formed in the bank 12. In thisexample, each of pixels 34 includes four sub-pixels 36 of RGBW. FIG. 8illustrates a case in which the contact hole 32 is arranged in the bank12 between the pixels 34 adjacent to each other in a horizontaldirection, and FIG. 9 illustrates a case in which the contact hole 32 isarranged in the bank 12 between the pixels 34 adjacent to each other ina vertical direction.

SUMMARY OF THE INVENTION

The bank 12 in which the contact hole 32 is arranged as illustrated inFIGS. 8 and 9 has a portion requiring a width larger than the bank inwhich the contact hole 32 is not arranged. That is, in the configurationwhere the contact hole 32 that connects the upper electrode 24 to thefeeder line 30 is formed in the bank 12, a width of the bank 12 becomeslarger than a size required for an original function of the bank 12, andthe miniaturization of the bank 12 is limited. This leads to such aproblem that the formation of the contact hole 32 is disadvantageous inthe high definition of the organic EL display device.

Also, as illustrated in FIGS. 8 and 9, the contact hole 32 may not bealways provided for each of the pixels depending on the conductivity ofthe upper electrode 24. However, in an image display device, since arraypitches of the pixels are made uniform within the display area for thepurpose of ensuring a display quality, the width and an area of the bank12 at a position where the contact hole 32 does not need to be arrangedfrom the viewpoint of electric characteristics are formed as large asthose of the bank 12 at a position where the contact hole 32 isprovided. As a result, an useless non-emitting area becomes large.

Specifically, when a pixel pitch in the horizontal direction is x, and apixel pitch in the vertical direction is y in a pixel array of a matrixillustrated in FIGS. 8 and 9, x becomes larger than x when the contacthole 32 is not arranged in the bank 12 in the configuration illustratedin FIG. 8, and y becomes larger than y when the contact hole 32 is notarranged in the bank 12 in the configuration illustrated in FIG. 9. Anincrease in the pixel pitch is disadvantageous in higher definition, andthe increase in the pixel pitch is caused by an increase in the width ofthe bank 12, which means an increase in the non-emitting area.

The present invention aims at providing an organic EL display devicethat suppresses shading, and obtains a high quality image whilemaintaining a high opening ratio of a pixel.

(1) According to the present invention, there is provided an organic ELdisplay device in which a plurality of pixels each including at leastone organic light emitting element formed in an opening area surroundedby a partition, and having a common shape are two-dimensionally arrayed,in which a feeder line is formed on a substrate, and receives areference potential for driving the organic light emitting element, inwhich the organic light emitting element is formed on the substratewhere the feeder line is formed, and has a structure in which a lowerelectrode, an organic material layer, and an upper electrode common tothe plurality of pixels are laminated on each other in the order fromthe bottom, and in which some of the plurality of pixels are irregularpixels in which a perpendicular interconnection that penetrates throughthe organic material layer, and electrically connects the upperelectrode to the feeder line is formed within the opening area.

(2) In the organic EL display device according to the above item (1),each of the pixels can include four of the opening areas that emit lightof red, green, blue, and white, and in the irregular pixels, theperpendicular interconnection can be formed in all or a part of theopening area of the white light emission instead of the structure of theorganic light emitting element.

(3) In the organic EL display device according to the above item (1),each of the pixels can include three of the opening areas that emitlight of red, green, and blue, and in the irregular pixels, theperpendicular line can be formed in all or a part of the opening area ofthe blue light emission instead of the structure of the organic lightemitting element.

(4) The configuration according to the above items (1) to (3) issuitable for the organic EL display device in which the upper electrodeis formed of a transparent conductive film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating a general configuration of anorganic EL display device according to a first embodiment of the presentinvention;

FIG. 2 is a schematic partial plan view of a pixel array portion of theorganic EL display device according to the first embodiment of thepresent invention;

FIG. 3 is a schematic partial cross-sectional view of the pixel arrayportion of the organic EL display device according to the firstembodiment of the present invention;

FIGS. 4A to 4C are schematic vertical cross-sectional views of mainsteps in a process for forming a cathode contact;

FIG. 5 is a schematic plan view of an irregular pixel in an organic ELdisplay device according to a second embodiment of the presentinvention;

FIG. 6 is a schematic partial plan view of a pixel array portion in anorganic EL display device according to a third embodiment of the presentinvention;

FIG. 7 is a schematic partial cross-sectional view of a display area ofa TFT substrate in a related art organic EL display device;

FIG. 8 is a plan view illustrating a part of a display area in therelated art organic EL display device in which a contact hole thatconnects an upper electrode of an OLED to a feeder line is formed in abank between adjacent pixels in a horizontal direction; and

FIG. 9 is a plan view illustrating a part of a display area in therelated art organic EL display device in which a contact hole thatconnects an upper electrode of an OLED to a feeder line is formed in abank between adjacent pixels in a vertical direction.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the accompanying drawings.

First Embodiment

An organic EL display device is an active matrix display device, and isincorporated into a television, a personal computer, a mobile terminal,and a cellular phone as a display panel. FIG. 1 is a schematic viewillustrating a general configuration of an organic EL display device 60according to a first embodiment of the present invention. The organic ELdisplay device 60 includes a pixel array portion 62 which is a displayarea for displaying an image, and a drive portion that drives the pixelarray portion 62.

In the pixel array portion 62, OLEDs 64 and pixel circuits 66 arearranged in a matrix in correspondence with pixels (or sub-pixels). Eachof the pixel circuits 66 includes plural thin film transistors (TFT) 68,70, and a capacitor 72. An anode electrode of each OLED 64 is connectedto the drive TFT 70. Also, cathode electrodes of all the OLEDs 64 areconfigured by a common electrode as will be described later.

On the other hand, the drive portion includes a scanning line drivercircuit 80, a video line driver circuit 82, a drive power supply circuit84, a reference power supply circuit 86, and a control device 88. Thedrive portion drives the pixel circuits 66, and controls the lightemission of the OLED 64.

The scanning line driver circuit 80 is connected to scanning lines 90provided for each line (pixel row) of the pixels in the horizontaldirection. The scanning line driver circuit 80 selects the scanninglines 90 according to a timing signal input from the control device 88in order, and applies a voltage for turning on the lighting TFT 68 tothe selected scanning line 90.

The video line driver circuit 82 is connected to video signal lines 92provided for each line (pixel column) of the pixels in the verticaldirection. The video line driver circuit 82 receives a video signal fromthe control device 88, and outputs a voltage corresponding to the videosignal of the selected pixel row to each of the video signal lines 92according to the selection of the scanning lines 90 by the scanning linedriver circuit 80. The voltage is written in the capacitor 72 throughthe lighting TFT 68 on the selected pixel row. The drive TFT 70 suppliesa current corresponding to the written voltage to the OLED 64 with theresult that the OLED 64 of the pixel corresponding to the selectedscanning line 90 emits light.

The control device 88 includes an arithmetic processing circuit such asa CPU (central processing unit), and a storage unit formed of a memoryelement such as an ROM (read only memory) or an RAM (random accessmemory). The control device 88 receives the video signal. For example,when the organic EL display device 60 configures a display portion of acomputer or a mobile terminal, the video signal is input to the organicEL display device 60 from a computer of a main body. Also, when theorganic EL display device 60 configures a television receiver, the videosignal is received by an antenna or a tuner not shown. The controldevice 88 executes various processing by allowing the CPU to read andexecute a program stored in the memory. Specifically, the control device88 conducts various image signal processing such as color tuning on thevideo signal, and outputs the video signal to the video line drivercircuit 82. Also, the control device 88 generates a timing signal forsynchronizing the scanning line driver circuit 80 or the video linedriver circuit 82 on the basis of the input video signal, and outputsthe timing signal toward those circuits.

The drive power supply circuit 84 is connected to a drive power supplyline 94 disposed for each of the pixel columns, and supplies a currentto the OLED 64 through the drive power supply line 94 and the drive TFT70 of the selected pixel row.

The reference power supply circuit 86 gives a reference potential to acommon electrode (not shown) configuring the cathode electrodes of theOLEDs 64, and a reference power supply line 96. The reference potentialcan be set to a ground potential.

The reference power supply line 96 (feeder line) is arranged across thepixel array portion 62, and connected to the cathode electrode of someOLEDs 64 within the pixel array portion 62. In order to reduce a wiringresistance from the reference power supply circuit 86 to the cathodeelectrode of the OLED 64, it is preferable that the reference powersupply line 96 extends along short sides of the pixel array portion 62.In this embodiment, the pixel array portion 62 is a vertically longrectangular, and the reference power supply line 96 is arranged in thehorizontal direction in correspondence with the configuration of thepixel array portion 62. FIG. 1 illustrates a configuration in which onereference power supply line 96 is arranged in the pixel array portion62, and connected to one OLED 64 as an example of the configuration inwhich the reference power supply line 96 is connected to only a part ofthe OLEDs 64 as described above. Both ends of the reference power supplyline 96 can be connected to the reference power supply circuit 86.However, in FIG. 1, for convenience of illustration, only one end of thereference power supply line 96 is connected to the reference powersupply circuit 86.

The supply of the reference potential to the cathode electrode of theOLED 64 with the use of the reference power supply line 96 will bedescribed in more detail. FIG. 2 is a schematic partial plan view of thepixel array portion 62 of the organic EL display device 60. Each ofpixels 100 includes four sub-pixels of RGBW which are Bayer-arrayed.Specifically, four opening areas 102 aligned two by two in thehorizontal direction and the vertical direction correspond to the foursub-pixels 104. An R sub-pixel 104 r and a B sub-pixel 104 b arearranged on one diagonal line of a rectangle formed by the four openingareas, and a G sub-pixel 104 g and a W sub-pixel 104 w are arranged onanother diagonal line thereof. In this embodiment, the respectiveopening areas 102 are designed with the identical shape and size.

One OLED 64 is formed in each of the opening areas 102 formed in theinsulating layer. In this example, four kinds of light emission colorsdifferent in each of the sub-pixels 104 are obtained by forming fourkinds of OLEDs 64 that emit light of different colors, or combining theOLED 64 that emits light of, for example, white, and a color filter.

A bank 106 is formed around each of the opening areas 102. That is, thebank 106 partitions the respective opening areas 102 adjacent to eachother in the horizontal direction, and partitions the respective openingareas 102 adjacent to each other in the vertical direction. Also, thebank 106 is formed of an insulating layer, and covers an edge of thelower electrode formed in each of the pixels to prevent short-circuitingbetween the lower electrode and the upper electrode. A width of the bank106 can be set to a size sufficient to perform a function of the bank asa partition for separating and forming the OLEDs 64, and does notrequire a size as large as the contact hole can be formed as describedin the related art. A width W_(BH) of a portion in the bank 106 whichpartitions the respective opening areas 102 aligned in the horizontaldirection, and a width W_(BV) of a portion in the bank 106 whichpartitions the respective opening areas 102 aligned in the verticaldirection can be made identical with each other between the respectivearbitrary opening areas 102. Also, the width W_(BH) and the width W_(BV)can be basically set to the same value.

The above-mentioned pixels 100 are basic pixels in the pixel arrayportion 62, and at least majority of the pixels configuring the pixelarray portion 62 includes the basic pixels 100. On the other hand, somepixels of the pixel array portion 62 are configured by irregular pixels100 a having a structure in which the basic pixel 100 are changed. Ineach of the irregular pixels 100 a, a perpendicular interconnection(cathode contact) is formed in an opening area within the irregularpixel 100 a. The perpendicular interconnection penetrates through theorganic material layer configuring the OLED 64 and electrically connectsthe cathode electrode, which is the upper electrode, and the referencepower supply line 96. In the irregular pixel 100 a according to thisembodiment, a cathode contact is formed in an opening area 102 acorresponding to the W sub-pixel 104 w in the basic pixel 100 instead ofthe structure of the organic light emitting element. The otherconfigurations of the irregular pixel 100 a are identical with those ofthe basic pixels 100. Hence, pixel pitches x′ in the horizontaldirection, and pixel pitches y′ in the vertical direction are uniform inthe pixel array portion 62.

FIG. 3 is a schematic partial cross-sectional view of the pixel arrayportion 62 of the organic EL display device 60, which illustrates avertical cross-section of the pixel array portion taken along a lineIII-III in the horizontal direction illustrated in FIG. 2. The organicEL display device 60 has a structure in which a TFT substrate 110 and acounter substrate 112 are bonded with each other with a filler layer 114sandwiched therebetween. In this embodiment, the pixel array portion isof a top emission type, the OLED 64 that is a light emitting portion isformed on the TFT substrate 110, and a light generated by the OLED isemitted from the counter substrate 112. That is, in FIG. 3, the light ofthe OLED is emitted upward. Also, a coloring system in the organic ELdisplay device 60 illustrated in FIG. 3 is a color filter system inwhich a white light is generated by the OLED, and the white light passesthrough the color filter to obtain the respective colors of RGB. In theW sub-pixel 104 w, no color filter is arranged, and the white light ofthe OLED is extracted as it is.

In the TFT substrate 110, for example, a circuit layer 122, aninsulating film. 124, the bank 106, the OLED 64, a cathode contact 126,and a sealing film 128 are laminated on a glass substrate 120.

The circuit layer 122 includes the pixel circuits 66, the scanning lines90, the video signal lines 92, the drive power supply line 94, and thereference power supply line 96 as described above, and is formed on asurface of the glass substrate 120. FIG. 3 illustrates only thereference power supply line 96 in the circuit layer 122. Since thecircuit layer 122 is located in the rear of the OLED 64 in the organicEL display device 60 of the top emission type when viewed from thecounter substrate 112 side which is a display surface, the circuit layer122 can be made of an opaque material. In particular, the various linessuch as the reference power supply line 96 can be made of metal high inconductivity as compared with a transparent conductive material such asITO (Indium Tin Oxide) or IZO (Indium Zinc Oxide), and decrease theresistance.

The OLED 64 has a structure in which a lower electrode 130, an organicmaterial layer 132, and an upper electrode 134 are laminated on eachother in order from the bottom. The organic material layer 132 includesa hole transport layer, a light emitting layer, and an electrontransport layer.

In this embodiment, the lower electrode 130 and the upper electrode 134configure the anode electrode and the cathode electrode of the OLED 64,respectively, and the light emission in the light emitting layer iscontrolled according to an electric signal applied between the lowerelectrode 130 and the upper electrode 134.

The lower electrodes 130 are separated for each of the pixels. The lowerelectrode 130 is made of ITO or IZO. The lower electrode 130 iselectrically connected to the TFT (the drive TFT 70 illustrated inFIG. 1) formed in the circuit layer 122 through a contact hole (notshown), and supplied with a current corresponding to the video signal bythe drive portion and the pixel circuit.

In this embodiment, the organic EL display device 60 is of the topemission type, and the lower electrode 130 can have a double-layerstructure in which a transparent conductive film is laminated on areflective layer made of a material high in optical reflectivity. Forexample, the reflective layer can be made of aluminum (Al) or silver(Ag), and reflects the light from the light emitting layer to thedisplay surface, that is, the counter substrate 112 side.

The upper electrode 134 is a common electrode that is basicallycontinuously formed over the pixels of the overall pixel array portion62. The upper electrode 134 is made of a transparent electrode materialsuch as ITO or IZO.

An end of the upper electrode 134 is connected to the reference powersupply circuit 86 illustrated in FIG. 1 through the line, and appliedwith a reference potential from the reference power supply circuit 86.

Further, the upper electrode 134 is connected to the reference powersupply line 96 by the cathode contact 126 formed in the opening area 102a located at a position corresponding to the W sub-pixel in the pixel100, in the irregular pixel 100 a, and applied with a referencepotential from the reference power supply circuit 86 through thereference power supply line 96. As described above, the reference powersupply line 96 is made of metal and can decrease the resistance, and avoltage drop between the reference power supply circuit 86 and thecathode contact 126 due to the reference power supply line 96 is smallerthan a voltage drop in the upper electrode 134. Under the circumstances,the irregular pixel 100 a is arranged so that the uniformity of thepotential of the upper electrode 134 in the pixel array portion 62 isimproved by the application of the reference potential through thecathode contact 126, and the shading of the brightness of the OLED 64 issuppressed.

As described above, with the use of the cathode contact 126 and thereference power supply line 96, even if the upper electrode 134 isthinned, the shading can be suppressed. Hence, since the upper electrode134 can be thinned to improve the transmittance of the upper electrode134, a drive electric power of the OLED 64 for obtaining a desireddisplay brightness can be reduced.

The cathode contact 126 is made of a conductive material filled in acontact hole 136 that penetrates through the insulating film 124, alower electrode 130 a, and a conductive material of the upper electrode134 filled in a hole that penetrates through the organic material layer132.

The sealing film 128 is laminated on the overall surface of the pixelarray portion 62 where the OLEDs 64 are formed. The sealing film 128 hasa function of blocking the transmission of moisture contained in thefiller layer 114 to protect the OLEDs 64.

The counter substrate 112 has a structure in which a color filter 142 islaminated on a transparent substrate such as a glass substrate 140. Forexample, in the cross-section illustrated in FIG. 3, the color filter142 that transmits through a wavelength region of red is arranged at aposition of the R sub-pixel 104 r. As has already been described, nocolor filter 142 is arranged in the W sub-pixel 104 w. A black matrix144 is arranged in a boundary of the color filter 142.

FIGS. 4A to 4C illustrate a schematic process flow illustrating a methodof forming the cathode contact 126, and FIGS. 4A to 4C are respectiveschematic vertical cross-sectional views of main manufacturing steps ina portion related to the cathode contact 126 in the opening area 102 aof the irregular pixel 100 a of FIG. 3.

FIG. 4A illustrates a state in which the circuit layer 122, theinsulating film 124, the lower electrode 130, the bank 106, and theorganic material layer 132 are sequentially formed over the glasssubstrate 120. The formation of those respective layers can be basicallyconducted in the same manner as the normal opening areas 102 where theOLEDs 64 are formed, or the related art. In the opening area 102 a, thereference power supply line 96 is arranged below the lower electrode 130a as the circuit layer 122, and the contact hole 136 is formed above thereference power supply line 96 in the insulating film 124. Incidentally,in the normal opening area 102, the contact hole for connecting thelower electrode 130 to the drive TFT 70 is formed in the insulating film124, and instead, the contact hole 136 is formed in the opening area 102a. The contact hole in the normal opening area and the contact hole 136in the opening area 102 a can be formed in the same step. The contacthole 136 is filled with a conductive material.

After the contact hole 136 has been formed in the insulating film 124, aconductive film forming the lower electrode 130 is laminated on thesurface of the insulating film 124, and patterned through thephotolithography to form the lower electrode 130 a separated from thelower electrode 130 of the adjacent opening area 102. Incidentally, thefilling of the above contact hole 136 with the conductive material canbe conducted in the step of laminating the conductive material formingthe lower electrode 130 a. That is, the conductive material forming thelower electrode 130 a is formed on the surface of the insulating film124 and also filled in the contact hole 136 to electrically connectbetween the reference power supply line 96 and the lower electrode 130a.

After the formation of the lower electrode 130 a, the bank 106 isformed, and the organic material layer 132 is laminated. FIG. 4Aillustrates a state in which the above step has been completed.

Then, a through-hole 150 is opened in the organic material layer 132 ofthe opening area 102 a (FIG. 4B). The through-hole 150 can be formed by,for example, removing the organic material layer 132 with theirradiation of a laser beam 152. After the formation of the through-hole150, the conductive film is laminated to form the upper electrode 134(FIG. 4C). The conductive film of the upper electrode 134 is filled inthe through-hole 150, and electrically connected to the lower electrode130 a that is exposed from a bottom of the through-hole 150. With theabove configuration, as perpendicular interconnection that penetratesthrough the organic material layer 132 and electrically connects theupper electrode 134 and the reference power supply line 96, the cathodecontact 126 is formed in the opening area 102 a.

When the organic material layer 132 is painted for each of the openingareas 102 through the ink jet system, the organic material layer 132 isnot formed in the opening area 102 a of the irregular pixel 100 a inadvance, as a result of which the removal step can be omitted. Also,when the organic material layer 132 is formed by vapor deposition, theopening area 102 a can be put into an area in which the organic materiallayer 132 is not formed with the use of a fine metal mask.

In the above-mentioned organic EL display device 60, a part of thepixels that are two-dimensionally arrayed in the pixel array portion 62is the irregular pixel 100 a. A position of the irregular pixel 100 a inthe pixel array portion 62 is stored in a memory of the control device88 in advance. The control device 88 generates a signal representing abrightness value of the sub-pixels 104 in each of the pixels on thebasis of the input video signal, and outputs the signal to the videoline driver circuit 82. In this situation, the control device 88determines whether the pixel represented by the input video signal isthe basic pixels 100 or the irregular pixel 100 a, with reference toinformation on the position of the irregular pixel 100 a stored in thememory. Then, the control device 88 converts the video signalcorresponding to the position of the basic pixel 100 into four kinds ofcolor component signals of RGBW, and also converts the video signalcorresponding to the position of the irregular pixel 100 a into threekinds of color component signals of RGB. In the conversion, theintensity of the respective component signals of RGBW is determined sothat the color and the brightness represented by the input video signalare represented by the composition of the light emission of RGBW colorsin the basic pixel 100. In the irregular pixel 100 a, the intensity ofthe respective component signals of RGB is determined so that the colorand the brightness are represented by the composition of the lightemission of RGB colors. As a result, the same display characteristic isbasically realized between the pixels 100 and the irregular pixels 100a.

Second Embodiment

A description will be given of the organic EL display device 60according to a second embodiment of the present invention below. In thisembodiment, the components common to those in the first embodiment aredenoted by identical symbols, and a description of those components willbe basically omitted, and differences from the first embodiment will bemainly described.

Each of the pixels 100 according the second embodiment includes foursub-pixels of RGBW which are Bayer-arrayed as in the first embodiment.Differences between the second embodiment and the first embodimentreside in the structure of the irregular pixel. FIG. 5 is a schematicplan view of an irregular pixel 100 b according to the secondembodiment. In the irregular pixel 100 b, the cathode contact 126 isformed in a part of an area 160 corresponding to an opening area of theW sub-pixel 104 w of each basic pixel 100 instead of the structure ofthe organic light emitting element. Specifically, the area 160 ispartitioned into two areas 160 a and 160 b by a bank 162, and the OLED64 of the white light emission is formed, for example, in the area 160 aas with the basic pixel 100. On the other hand, the cathode contact 126is formed in the area 160 b without provision of the organic materiallayer 132.

In this embodiment, the control device 88 converts the video signalcorresponding to the position of the irregular pixel 100 b into fourkinds of the color component signals of RGBW. In this situation, that anarea of the W sub-pixel 104 w in the irregular pixel 100 b is smallerthan the basis pixel 100 is taken into consideration. For example, thebrightness reduction corresponding to a reduction of the area of the Wsub-pixel 104 w can be compensated by increasing the light emissionintensity of the RGB sub-pixels 104, or can be compensated by increasinga current density of the OLED in the W sub-pixel 104 w.

Third Embodiment

A description will be given of the organic EL display device 60according a third embodiment of the present invention. In thisembodiment, the components common to those in the first embodiment aredenoted by identical symbols, and a description of those components willbe basically omitted, and differences from the first embodiment will bemainly described.

FIG. 6 is a schematic partial plan view of a pixel array portion 62 inan organic EL display device 60 according to this embodiment. Thisembodiment is different from the first embodiment in that a basic pixel200 includes three sub-pixels of RGB, and the cathode contact 126 isformed in an opening area 102 b located at a position in an irregularpixel 200 a corresponding to the B sub-pixel in the basic pixel 200.

In this embodiment, the irregular pixel 200 a includes two sub-pixels ofRG. For that reason, a deficit of the B sub-pixel caused by theprovision of the cathode contact 126 cannot be compensated by signalprocessing. However, since B is a color lowest in the visual sensitivityamong RGB, a configuration in which the B sub-pixel forms the formationarea of the cathode contact 126 hardly deteriorates the image quality.In particular, if the number of irregular pixels 200 a is very small inthe pixel array portion 62, the image quality deterioration is notnoticeable. On the other hand, with the provision of the cathode contact126, as in the first and second embodiments, the shading is suppressed,and the power consumption in the OLED can be reduced.

In the above respective embodiments, the organic EL display device 60 isof the top emission type. However, the present invention intended tosubstantially reduce the resistance of the upper electrode 134 using thereference power supply line 96 and the cathode contact 126 can be alsoapplied to the organic EL display device 60 of a bottom emission type.For example, in a large-area display device, with the application of theconfiguration of the present invention, the shading can be furtherpreferably suppressed as compared with a case in which the upperelectrode 134 is merely thickened to reduce the resistance.

According to the above-mentioned present invention using theembodiments, the upper electrode is connected to the feeder line withinthe display area, thereby being capable of suppressing shading. Sincethe connection between the upper electrode and the feeder line isconducted by the opening areas of some pixels, there is no need toincrease the width of the bank, the high opening ratio of the pixel canbe maintained from the viewpoint of the overall display area, and theresolution is improved.

While there have been described what are at present considered to becertain embodiments of the invention, it will be understood that variousmodifications may be made thereto, and it is intended that the appendedclaims cover all such modifications as fall within the true spirit andscope of the invention.

What is claimed is:
 1. An organic electroluminescent (EL) display devicein which a plurality of pixels each including an organic light emittingelement formed in an opening area are two-dimensionally arrayed, thedevice comprising a feeder line formed on a substrate, and receiving areference potential for driving the organic light emitting element,wherein the organic light emitting element is formed on the substratewhere the feeder line is formed, and has a structure in which a lowerelectrode provided for each pixel, an organic material layer, and anupper electrode common to the plurality of pixels are laminated on eachother, in the order from the bottom, the plurality of pixels includesbasic pixels and irregular pixels, each of the irregular pixels has afirst sub pixel and at least one second sub pixel, the first sub pixelincludes a perpendicular interconnection that penetrates through theorganic material layer and electrically connects the upper electrode tothe feeder line is formed within the opening area, the upper electrodeis on and in physical contact with the lower electrode at theperpendicular interconnection in the first sub pixel, the feeder line iselectrically connected to the upper electrode via the lower electrode atthe perpendicular interconnection in the first sub pixel, the at leastone second sub pixel does not include the perpendicular interconnectionand each of the basic pixels does not include the perpendicularinterconnection.
 2. The organic EL display device according to claim 1,wherein each of the pixels include four of the opening areas that emitlight of red, green, blue, and white, wherein in the irregular pixels,the perpendicular interconnection is formed in all or a part of theopening area of the white light emission instead of the structure of theorganic light emitting element.
 3. The organic EL display deviceaccording to claim 1, wherein each of the pixels include three of theopening areas that emit light of red, green, and blue, and wherein thein the irregular pixels, the perpendicular interconnection is formed inall or a part of the opening area of the blue light emission instead ofthe structure of the organic light emitting element.
 4. The organic ELdisplay device according to claim 1, wherein the upper electrode isformed of a transparent conductive film.